if your bases are white in places meaning they are dried out then yes you should get a stone grind. The white areas are dried out areas, they are not going to absorb wax. You don't need to do this every time you wax your skis but this does mean that you should wax your skis more often because they are drying out.

when you get your skis ground you are removing much of the wax in the bases. In order to prevent base burn as its called, many, many coats of wax are great. See if your shop has a hotbox and have them run your sticks through a cycle in there.

I've been wondering will the grinding help alsi skis with extruded bases? I have Line anthems and they are bit slow. Will the grinding make em faster and or help them hold wax better? So will my skis benefit from grinding or is it just waste of money?

Extruded bases do not absorb wax well (read: at all) when compared to sintered bases. They glide decently on their own for ease of use/maintenance (an extruded base glides better than a dried out sintered base, but not better than a properly maintained sintered base). Maxi-glide makes a rub-on wax specifically for extruded bases, but as it cannot be absorbed it will only last you a couple of runs.

Getting a stone grind with the appropriate pattern for the temperature you are mostly going to be in will help you out, but it won't be nearly as good as a properly maintained sintered base. Generally speaking, cold conditions = tight/fine pattern, warm conditions = spaced/deeper pattern.